My option is/why/ and not how often so I picked Rarely. I only check it when I expect email that doesn't show up in my Inbox. Happens now and then that I need to reset a password or sign up to a new site that Google mail may not trust or something. If the confirmation email doesn't show up in the inbox in a reasonable amount of time I'll check the Spam folder. Sometimes it's there and I make a rule. Sometimes the site is just slow to email me. Either way, the look at what the spam filter caught is usually amusing.

Been working well for a decade. The neat thing is that 90% of the stuff that needs to be rejected can be done without any spam analysis at all. I only call my spamassassin checks *AFTER* vetting things through MimeDefang. Why waste the CPU cycles? RBLs, Pretending to be from my domain, mail to system accounts, invalid HELO (not FQDN or IP address - single words are very popular with spammers/botnets), RFC1918 HELO addresses, etc. After that, they then go through my spamassassin process, which has been collecting bayes data for several years. The community provided spamassassin rules are kept up to date, and I have a Nagios process that also ensures they are up to date (check_sa-update on nagios exchange. Written by yours truly).

I'd put my system, based on MimeDefang, Spamassassin, clam, etc against barracuda any day. I bet I have a lot less false positives (0 the past year, 1 every couple of months while tuning at my last company), and use a whole lot less CPU by discarding obvious garbage that doesn't need to be processed by spamassassin.

The most recent thing is the "Hello" stuff from legitimate mail accounts. The spammers are using active exploits the past few years to slip through filters, but they still don't get in. I should relabel my spam folder to "Friends with compromised accounts" Everything else scores off the charts and is discarded.

I am not the AC you replied to, but I have tried being friendly and letting people know that they sent to the wrong address.

No good deed goes unpunished. The responses tend to be abusive, threatening or both, blaming the recipient for both obtaining the mail, reading some of it, and the capital offense of implying that the sender might have made a mistake.

If they're stupid enough to send e-mail to the wrong address, the risk is that they're also stupid enough to think that you were the one who caused the problem.